Knife blade type switch



March 26, 1963 R. H. LAMBERT ETAL. 3,083,271

KNIFE BLADE TYPE SWITCH Filed June 9, 1961 A V4@ V//A United States Patent 3,083,271 KNIFE BLADE TYPE SWITCH Richard H. Lambert, New Berlin, and Donald R. Krombos, Greenfield, Wis., assignors to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Filed June 9, 1961, Ser. No. 116,002 6 Ciaims. {CL 20e- 2) This invention relates to electric circuit interrupters and more particularly to a new and improved knife blade type switch assembly employing novel short circuiting means.

lt is desirable to detachably mount electrical devices such as integrating, indicating and/or recording instruments and relays on supporting structures. These supporting structures usually include casings proportioned to receive the electrical instruments. In order to permit ready removal of the electrical instruments from the casing, switch means are provided including parts carried by the instruments and parts on the casings. By actuation of the switch means, conductors secured to the casings and conductors secured to the instruments may be mechanically and electrically connected and disconnected. When the switch means is in disconnected position, the electrical instruments may be readily removed from the casing of the supporting structures.

Preferably the circuit interrupters take the form of knife blade type switches having contact jaws positioned on one of the relatively movable parts, such as the instruments and having knife blades pivotally secured to the remaining parts, `such as the casings, for rotation into and out of engagement with the contact jaws when the instruments are in operative positions within the casings. instruments often include circuits employing current transformers which should never be open circuited.

In accordance with the invention, improved means are provided for maintaining the required condition of such electrical circuits despite movement of the instrument with respect to its casing. The disclosed electric switch cornprises a pair of cooperating relatively movable contacts with one of the contacts comprising a pair of spaced oontact elements. A pair of bridging contacts are mounted on juxtaposed surfaces of the contact elements. The bridging contacts are disposed to engage each other in circuit open position of the movable contacts. Means are provided for separating these bridging contacts after engagement of the movable contacts.

lt is, therefore, one object of this invention to provide a new and improved electrical assembly including means for detachably supporting an electrical instrument.

Another object of this invention is toy provide a new and improved electrical assembly for detachably supporting an electrical instrument with respect to its supporting structure without modifying a desired condition of an electric circuit associated with the electrical assemb-ly.

A further object of this invention is to provide a new and improved knife blade type switch employing short circuiting means arranged on thel movable knife blade member.

Gbjects and advantages other than those set forth will be apparent from the following description when read in connection with the accompanying drawing, in which:

FIG. l is an illustration partly in section of an electric switch embodying the present invention taken along the line I-l of FiG. 2;

FIG. 2 is a cross sectional View of the structurey shown in FG. l taken along the line il-llg and FIG. 3 is a cross sectional view taken along the line lil-HI of FIG. 1.

Referring to FIGS. 1-3 of the drawing by characters of reference, the electric switch assembly comprises a relatively stationary supporting structure in the form of a casing 10 which is formed of a continuous wall 11 having a back closure (not shown) secured thereto. A relatively movable electrical assembly 12 is mounted for movement into and out of casing 1); An electric switch illustrated as a knife blade type comprising a pair of U-shaped hinge terminal or current conducting members 13 has a knife blade 14 pivotal-ly mounted on hinge members 13 for rotation about a common axis or pin means 15. Contact terminal or stationary current c-onducting jaw members 16 are arranged on the electrical assembly 12. The current conducting jaw members 16 are disposed on one side of the hinge members 13 in position to be engaged by blade 14 when it is rotated to a closed circuit position.

The current conducting members 13 are shown as formed out of strips of suitable conducting material which are provided with apertures 18 for receiving terminals 19 which rigidly secure a base 33 in casing 10l to members 13. Members 13 are each provided with an aperture or bore 1S for receiving pin means 15.

Knife blade assembly 14 comprises a U-shaped current carrying member having a pair of spaced parallelly arranged contact legs or elements 20 and 21. Contact elements 2t) and 21 are provided with aligned apertures 22 and Z3 arranged to line up with bore 15 in each of the members 13 when -the knife blade assembly 14 is arranged for pivotal mounting on members 13.

The contact elements 20 and 21 of knife blade 14 are provided with a pair of resilient bridging contacts 24 and 25 mounted to extend from juxtaposed surfaces 26 and 27 thereof. The bridging contacts 24 and 25 are so disposed that they engage each other in circuit open position of the pai-r of movable Contact elements 20 and 21.

As shown in FIG. l, contact elements 20 and 21 pivot clockwise from the switch closed position shown to switch open position about pin means 15. Each of the contact elements is provided with a handle 28 made out of suitable insulating material such as plastic and define an identification card holder slot 29. Each handle 28 is provided with an aperture 39 which is aligned with the apertures in similar handles for receiving a shaft or pin 31 4therethrough for multiple gauging, if required. At the current conducting end of each of the contact elements 20 and 21 is provided an arcing tip 32 which may -ibe made of the same tempered copper of elements 20 and 21 or of any other suitable conductive arc resistance material.

The movable current conducting contact elements 20 and 21 cooperate with the jaw contact members 16 mounted on the movable instrument chassis 33. These jaw contact members 16 are formed out of strips of suitable conducting material which are provided with apertures 1S for receiving terminals 19 which rigidly secure chassis 33 to members 16. Members 16 comprise jaw contacts 34 and 35 for cooperating with contact elements 2d and 21, respectively. I aw contacts 34 and 3S comprise U-'shaped members for engaging between their legs the contact elements 20 and 21 of the knife blade type switch.

Arranged between the jaw contacts 34 and 35 is an insulating barrier 38 secured to the movable part of the instrument chassis 33 by terminal 19. This barrier is shown as being U-shaped with one of its legs .39 being arranged to separate the resilient bridging contacts 24 and 25 upon predetermined movement of contact elements 2d and 21 in closing direction.

According to the present invention when the instrument chassis 33 is moved in-to casing 10 the knife blade y14 comprising the relatively movable contacts may be rotated counterclockwise as shown in FIG. 1 into Vengagement with the relatively stationary jaw contact members 34 and 35. If the instrument supported on the chassis 33 and casing l is energized atleast in part from a current transformer (not shown) it is desirable `that removal of the instrument should not open the circuit energized by the current transformer. To this end, the invention provides the resilient short circuiting bridging contacts 24 and 25 mounted on the juxtaposed surfaces of contact elements 20 and 21 which are employed for completing the circuit across the secondary winding of `the current transformer.

As shown in FIG. 1 the bridging contacts are positioned directly beneath the contact engaging portion of the knife blade 14. The bridging contacts 2d and 2.5' are in engagement with each other in a switch closing operation until after the contact elements 2t) and 2.1 have electrically engaged with the jaw contacts '3ft and 35. After such engagement and upon further movement of contact elements in switch closing direction the insulating leg 39 of barrier 38 causes disengagement of the bridging contacts 24 and 25.

In the switch closing operation after the tips 32 of contact elements 2@ and Z1 have engaged the jaw contacts 34 and 35 of jaw contact members i6 and before the insulating leg 39 of barrier 38 has separated the bridging contacts 24 and 25, `the electrical circuit connected to the contact elements `2d and 25 through the casing and the electrical equipment and circuits connected through the instrument chassis 33 are all short circuited `by the bridging contacts 24 and 2S on the contact elements and 21. Only after further movement of the contact elements 2b and 21 in switchclosing direction and upon separation of the bridging contacts 24 and is this short circuit removed.

In a switch opening operation the bridging contacts 24 and '25 move away from leg 39 of barrier 38 and engage each other before contact elements 20 and 21 separate from jaw contacts 34 and 35. Thus, the circuits connected with casing 10 and contact elements 2t? and Z1 as well as the circuits and equipment connected with the instrument chassis are short circuited before the contact elements 20 and 21 separate from the jaw contacts 34- and 35.

has `been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of other appended claims.

Having now ,particularly described and ascertained the nature of our said invention and the manner in which it is to be performed, we declare that what We claim is:

1. In an electric switch the combination comprising a pair of cooperating relatively movable contacts, one of said contacts comprising a pair of spaced contact elements, a pair of bridging contacts mounted on juxtaposed sur- -faces of said elements, said bridging contacts being disposed to engage each other in circuit open position of said movable contacts, and means `for separating said bridging contacts after engagement of said movable contacts.

2. In an electric switch the combination comprising a pair of cooperating relatively movable contacts, one of said contacts comprising a pair of spaced Contact elements, a pair of resilient bridging contacts mounted on Although but one embodiment of the present invention juxtaposed surfaces of said pair of elements, :said bridging contacts being disposed to engage each other in circuit open position of said movable contacts, and means for separating said bridging contacts after engagement of said movable contacts.

3. ln an electric switch the combination comprising two pairs of cooperating relatively movable contacts, the contacts of one of said pairs being spaced from each other, a pair of bridging elements mounted on juxtaposed surfaces of said one of said pairs of contacts, said bridging elements being disposed to engage each other in circuit open position of said pairs of movable contacts, and means for separating said bridging elements after engagement of said pairs of movable contacts, said bridging elements after engagement of said pairs of movable contacts but before separation of said bridging elements simultaneousiy short circuiting each of said pairs of movable contacts.

4. In an electric switch the combination comprising two pairs of cooperating relatively movable contacts each having contact engaging surfaces, the contacts of one of said pairs being spaced from each other, a pair of resilient bridging elements mounted on juxtaposed surfaces of said one of said pairs of movable contacts, said bridging elements being biased into engagement with each other in circuit open position of said pai-rs of movable contacts, and insulating means mounted between the other of said pairs of movable contacts for separating said bridging elements after engagement of said pairs of movable contacts.

5. A knife blade type switch comprising a rst pair of pivotally mounted contacts, the contacts of said rst pair being spaced from each other, a pair of resilient bridging elements mounted on juxtaposed surfaces of said first pair of contacts, said bridging elements being biased into engagement with each other in circuit open position of said switch, a second pair of contacts for engaging with said rst pair of contacts, each of said contacts of said second pair comprising a U-shaped member for engaging between its legs one of the contacts of said first pair of contacts, and insulating means arranged between said second pair of contacts for separating said bridging elements after engagement of said first and second pairs of contacts.

6. A knife blade type switch comprising a first pair of pivotally mounted contacts, the contacts of said first pair being spaced from each other, a pair of resilient bridging elements mounted on juxtaposed surfaces of said first pair of contacts, said bridging elements `being biased into engagement with each other in circuit open position of said switch, a second pair of Xedly mounted contacts for engaging with said rst pair of contacts, each of said contacts of said second pair :comprising a U- shaped member for engaging between its legs one of the contacts of said first pair, and insulating means xedly mounted between said second pair of contacts for separating said bridging elements after engagement of said first and second -pairs of contacts.

References Cited in the file of this patent UNITED STATES PATENTS 881,686 lI-oadiey Mar. 10, 1908 1,028,254 Murray June 4, 1912 2,066,299 Myliuo Dec. 29, 1936 2,908,775 Gilbert Cet. 13, 1959 

1. IN AN ELECTRIC SWITCH THE COMBINATION COMPRISING A PAIR OF COOPERATING RELATIVELY MOVABLE CONTACTS, ONE OF SAID CONTACTS COMPRISING A PAIR OF SPACED CONTACT ELEMENTS, A PAIR OF BRIDGING CONTACTS MOUNTED ON JUXTAPOSED SURFACES OF SAID ELEMENTS, SAID BRIDGING CONTACTS BEING DISPOSED TO ENGAGE EACH OTHER IN CIRCUIT OPEN POSITION OF SAID MOVABLE CONTACTS, AND MEANS FOR SEPARATING SAID BRIDGING CONTACTS AFTER ENGAGEMENT OF SAID MOVABLE CONTACTS. 